1. Field of Invention
The present invention relates to a method for forming film patterns, such as a conductive film wiring and a silicon film pattern, used for such as wirings of electrodes, antennas, electronic circuits, and integrated circuits, and an apparatus for forming the same. The present invention also relates to a conductive film wiring, an electro-optical apparatus, electronic equipment, and a non-contact card medium.
2. Description of Related Art
Currently, lithography methods, for example, are used in the manufacture of wirings used for electronic circuits, integrated circuits, or the like. In such lithography methods, a coating of a photosensitive material referred to as resist is applied on a substrate coated beforehand with a conductive film, a circuit pattern is irradiated and is developed, the conductive film is etched in accordance with the resist pattern and, therefore, a wiring is formed. This lithography method requires large-scale equipment, such as a vacuum apparatus, and complicated steps. Therefore, the efficiency of use of the material is about several percentages, the most of the material have to be discarded, and the manufacturing cost can be expensive.
On the other hand, U.S. Pat. No. 5,132,248 describes a method in which a substrate can be directly pattern-coated by an ink-jet method with liquid containing conductive fine particles being dispersed and, thereafter, a heat treatment or laser irradiation has been performed to convert into a conductive pattern. Using this method, there are merits that the photolithography becomes unnecessary, the process becomes simple by a large degree and, in addition, the usage of raw materials is reduced.
However, it is required that conductive fine particles are overlapped each other to some extent and a thick film can be formed in order to use as a wiring. In other words, when the conductive fine particles are not overlapped, the portions where the conductive fine particles are not made contact with each other bring about breaks, etc. Furthermore, when increase in thickness is insufficient, electrical resistance is increased and, therefore, the conductivity of the wiring becomes inferior.
However, regarding the method in which the substrate is directly pattern-coated by the ink-jet method with the liquid containing conductive fine particles being dispersed, since the liquid containing conductive fine particles being dispersed is used, there is a limit of the quantity of the conductive fine particles that can be applied by coating through discharge of a fixed quantity of the liquid from the viewpoint of viscosity, etc., during discharge. On the other hand, when it is intended to discharge the liquid in large quantities at a time, it becomes difficult to control the position of formation of the wiring. In addition, the line width of the wiring becomes large contrary to requirements for integration of electronic circuits, etc.
Accordingly, in order to properly perform conductive film wiring by the ink-jet method, as disclosed in Japanese Unexamined Patent Application Publication No. 59-75205, a method is suggested, in which banks (partition walls) are installed on a substrate and, therefore, the positions of the droplets discharged are controlled. By using the banks, even when discharge is performed with somewhat large quantities of discharge, the droplets discharged onto the substrate remain between the banks and, therefore, it is possible to form a wiring having a line width about 30 μm with the positional precision about 1 μm. However, such a bank has to be formed using photolithography and, therefore, an increase in cost is brought about.
It has also been suggested that a liquid material be selectively discharged by an ink-jet method onto a lyophilic portion of a substrate on which patterns of a liquid-repellent portion and the lyophilic portion were formed beforehand. In this case, since the liquid containing conductive fine particles being dispersed is likely to remain in the lyophilic portion, it is possible to form the wiring without forming banks while the positional precision is maintained.
However, regarding this method, since a step of forming patterns of the lyophilic portion and the liquid-repellent portion by using a mask, etc., is required and, in addition, a step of providing alignment marks for precisely applying a coating on the lyophilic pattern is also required, the process becomes complicated.
In addition, since the discharge is performed onto the lyophilic portion and, the droplets spread, it becomes difficult to form a conductive film with an increased film thickness. Consequently, it is considered to increase the number of discharges in order to increase the film thickness. However, it becomes difficult to collect the liquid within the lyophilic portion unless the liquid-repellent property of the liquid-repellent portion with respect to the liquid is increased by a large degree. Furthermore, the line width of the wiring to be formed is limited to the width of the lyophilic portion of the substrate.
As a method which does not require formation of the bank nor formation of the patterns of the liquid-repellent portion and the lyophilic portion, a method has been suggested which controlled the contact angle of liquid containing conductive fine particles being dispersed and a substrate at 30 degrees or more, but 60 degrees or less (Japanese Patent Application No. 2001-193679). In this invention, it is made possible to reduce wetting and spreading of the liquid after being hit onto the substrate and to increase the film thickness by controlling the contact angle at 30 degrees or more and, in addition, it is prevented by controlling the contact angle at 60 degrees or less that a droplet hit onto the substrate coalesces with a droplet having been already existed on the substrate so as to generate a puddle (bulge) and bring about problems such as breaks and short circuits.
In order to further avoid generation of bulges, the inventors of the present invention also suggested in the invention that the intervals between discharges be controlled and, therefore, overlapping of discharged droplets with each other was specified to become 1 to 10% of the diameter of the droplet. Furthermore, it was also suggested that after the discharged liquid was dried, another coating be applied thereon. In this case, since the portion where the liquid has been dried is lyophilic, the discharged liquid later is likely to remain at the portion where the liquid has been dried and, therefore, it becomes possible to further increase the film thickness.
Herein, the relationship between the bulge and the break and short circuit will be described. FIG. 13 shows the condition that bulges B1, B2, and B3 have been generated at conductive film wirings A1 to A4. As shown in FIG. 13, the bulge B1 generated on the conductive film wiring A1 contacts the adjacent conductive film wiring A2 and, therefore, the conductive film wiring A1 and the conductive film wiring A2 are short-circuited at X1. Since the bulge B1 is generated by surrounding droplets being attracted, a break has occurred at X2 in the conductive film wiring A1.
As described above, generation of the bulge brings about a fatal defect in performance of the conductive film wiring.
However, although the method according to the Japanese Patent Application No. 2001-193679 prevented generation of the bulge, it did not exhibit an adequate effect of preventing the liquid containing conductive fine particles being dispersed from wetting and spreading after being hit onto the substrate because the liquid-repellent property of the substrate was 60 degrees or less and was not so large. Consequently, further improvements have been required in order to meet the needs for the increase in film thickness and the decrease in line width.
Furthermore, in the case where another coating was applied after the liquid was dried, since the liquid-repellent property of the substrate was 60 degrees or less and was not so large, difference in the liquid-repellent property from the portion which became lyophilic after the liquid was dried was not adequate. Consequently, when the quantity of the liquid was excessive in application of another coating, there were problems in that the liquid did not remain at the portion where the liquid had been dried previously, and was likely to flow down to the substrate and, therefore, the line width was increased.
Next, in general, formation of patterns of silicon thin films applied to integrated circuits and thin film transistors is performed by forming amorphous or polysilicon films on all over the substrate surfaces by a thermal CVD method, a plasma CVD method, a photo-assisted CVD method, etc., and thereafter, by removing unnecessary portions of the silicon films by photolithography.
However, regarding formation of the silicon thin film pattern by these CVD methods and the photolithography, further improvements have been expected with respect to the following points in terms of the process.    (1) Since a vapor phase reaction is used, particles of silicon are generated in the vapor phase and, therefore, production yield is low due to pollution of the apparatus and generation of foreign matters.    (2) Since the raw material is gaseous, a silicon thin film with a uniform thickness is unlikely to be produced on a substrate having convexities and concavities on the surface.    (3) Since the formation speed of the film is low, the productivity is low.    (4) In the plasma CVD method, complicated and expensive high-frequency generators, vacuum apparatuses, etc., are required.    (5) Regarding photolithography, the process is complicated, the efficiency of use of the raw material is low, and large quantities of wastes, such as resists and etchants are generated.
In terms of the material, since gaseous silicon hydride having high toxicity and high reactivity is used, it is difficult to handle and, in addition, a hermetically sealed vacuum apparatus is required because of the material being gaseous. In general, these apparatuses are large-scale, the apparatuses themselves are expensive and, in addition, high cost of the product is brought about because a great deal of energy is consumed for a vacuum system and a plasma system.
On the other hand, a method for forming a silicon film pattern by simple steps with high precision has also been suggested, in which a coating of liquid containing an organic silicon compound has been selectively applied to only a lyophilic portion on a substrate on which patterns of a liquid-repellent portion and the lyophilic portion were formed beforehand by an ink-jet method and, thereafter, the liquid has been converted into a silicon film pattern by a heat treatment, etc.
However, regarding this method, since a step of forming patterns of the lyophilic portion and the liquid-repellent portion by using a mask, etc., is required and, in addition, a step of providing alignment marks for precisely applying a coating on the lyophilic pattern is also required, the process becomes complicated.
In addition, although the silicon film pattern is required to also have a somewhat large film thickness in order to keep the uniformity of the film, since the discharge is performed onto the lyophilic portion, the droplets spread by wetting and, therefore, it becomes difficult to increase the film thickness. Consequently, it is considered to increase the number of discharges in order to increase the film thickness. However, it becomes difficult to collect the liquid within the lyophilic portion unless the liquid-repellent property of the liquid-repellent portion with respect to the liquid is increased by a large degree. The width of the silicon film pattern formed is limited to the width of the lyophilic portion of the substrate.